kosiew commented on code in PR #16696:
URL: https://github.com/apache/datafusion/pull/16696#discussion_r2389739038
##########
datafusion/optimizer/tests/optimizer_integration.rs:
##########
@@ -478,6 +514,90 @@ fn
select_correlated_predicate_subquery_with_uppercase_ident() {
);
}
+#[test]
+fn recursive_cte_projection_pushdown() -> Result<()> {
+ // Test that projection pushdown works with recursive CTEs by ensuring
+ // only the required columns are projected from the base table, even when
+ // the CTE definition includes unused columns
+ let sql = "WITH RECURSIVE nodes AS (\
+ SELECT col_int32 AS id, col_utf8 AS name, col_uint32 AS extra FROM
test \
+ UNION ALL \
+ SELECT id + 1, name, extra FROM nodes WHERE id < 3\
+ ) SELECT id FROM nodes";
+ let plan = test_sql(sql)?;
+
+ // The optimizer successfully performs projection pushdown by only
selecting the needed
+ // columns from the base table and recursive table, eliminating unused
columns
+ assert_snapshot!(
+ format!("{plan}"),
+ @r#"SubqueryAlias: nodes
+ RecursiveQuery: is_distinct=false
+ Projection: test.col_int32 AS id
+ TableScan: test projection=[col_int32]
+ Projection: CAST(CAST(nodes.id AS Int64) + Int64(1) AS Int32)
+ Filter: nodes.id < Int32(3)
+ TableScan: nodes projection=[id]
+"#
+ );
+ Ok(())
+}
+
+#[test]
+fn recursive_cte_with_unused_columns() -> Result<()> {
Review Comment:
We don’t yet cover the “nested subquery disables pushdown” path—both
existing tests keep the recursive terms subquery-free. I’ll add a companion
test that embeds a SELECT … FROM (SELECT …) AS sub inside the CTE, then assert
that the resulting plan shows raw TableScan: test entries (no projection=[…])
to document the current bailout.
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